Fix pager test flackiness and add stress tests for echo_via_pager

CHANGES.rst

@@ -5,6 +5,13 @@ Version 8.4.2
 
 Unreleased
 
+-   Fix a race in ``echo_via_pager``'s exception-handling tests so they
+    pass deterministically under parallel execution and free-threaded
+    Python 3.14t, removing the workaround skip from :pr:`3470`.
+    :issue:`2899` :pr:`3499`
+-   The ``stress`` tox env now collects ``@pytest.mark.stress`` tests
+    from any test module. :pr:`3499`
+
 
 Version 8.4.1
 -------------

pyproject.toml

@@ -185,12 +185,11 @@ commands = [[
 ]]
 
 [tool.tox.env.stress]
-description = "stress tests for stream lifecycle race conditions"
+description = "high-iteration stress tests for race conditions"
 commands = [[
     "pytest", "-v", "--tb=short", "-x", "-m", "stress",
     "--basetemp={env_tmp_dir}",
     "--override-ini=addopts=",
-    "tests/test_stream_lifecycle.py",
     {replace = "posargs", default = [], extend = true},
 ]]
 

src/click/_compat.py

@@ -12,7 +12,6 @@
 
 CYGWIN = sys.platform.startswith("cygwin")
 WIN = sys.platform.startswith("win")
-MAC = sys.platform == "darwin"
 auto_wrap_for_ansi: t.Callable[[t.TextIO], t.TextIO] | None = None
 _ansi_re = re.compile(r"\033\[[;?0-9]*[a-zA-Z]")
 

tests/test_stream_lifecycle.py

@@ -484,7 +484,9 @@ def cli():
 # Category 6: Stress tests - high-iteration reproducers for race conditions
 #
 # These are marked with ``pytest.mark.stress`` so they can be included or
-# excluded independently. The CI workflow runs them in a separate job.
+# excluded independently. The ``tox -e stress`` env collects every
+# ``pytest.mark.stress`` test across the suite (not just this file), so
+# stress regressions for other components live alongside their unit tests.
 # ---------------------------------------------------------------------------
 
 

tests/test_utils.py

@@ -16,7 +16,6 @@
 
 import click._termui_impl
 import click.utils
-from click._compat import MAC
 from click._compat import WIN
 from click._utils import UNSET
 
@@ -286,6 +285,11 @@ def _test_gen_func():
 
 
 def _test_gen_func_fails():
+    raise RuntimeError("This is a test.")
+    yield  # unreachable, keeps this a generator function
+
+
+def _test_gen_func_yields_then_fails():
     yield "test"
     raise RuntimeError("This is a test.")
 
@@ -315,10 +319,6 @@ def _test_simulate_keyboard_interrupt(file=None):
 
 
 @pytest.mark.skipif(WIN, reason="Different behavior on windows.")
-@pytest.mark.skipif(
-    MAC and sys.version_info >= (3, 13) and not sys._is_gil_enabled(),
-    reason="Generator exception tests are flaky in Python 3.14t on macOS.",
-)
 @pytest.mark.parametrize(
     "pager_cmd", ["cat", "cat ", " cat ", "less", " less", " less "]
 )
@@ -456,6 +456,75 @@ def test_echo_via_pager(monkeypatch, capfd, pager_cmd, test, tmp_path):
     )
 
 
+@pytest.mark.skipif(WIN, reason="Different behavior on windows.")
+def test_echo_via_pager_yields_before_exception(monkeypatch, tmp_path):
+    """A generator that yields then raises: click writes the partial output to
+    the pager stream before propagating the exception.
+
+    The pager file content is intentionally NOT asserted: pipe-drain timing
+    between click and the pager subprocess is outside click's control
+    (#2899, #3470). Spying on ``MaybeStripAnsi.write`` records what click sent
+    to the pager, which is deterministic regardless of scheduling.
+    """
+    monkeypatch.setitem(os.environ, "PAGER", "cat")
+    monkeypatch.setattr(click._termui_impl, "isatty", lambda x: True)
+
+    writes: list[str] = []
+    real_write = click._termui_impl.MaybeStripAnsi.write
+
+    def spy(self, text):
+        writes.append(text)
+        return real_write(self, text)
+
+    monkeypatch.setattr(click._termui_impl.MaybeStripAnsi, "write", spy)
+
+    pager_out_tmp = tmp_path / "pager_out.txt"
+    with (
+        pager_out_tmp.open("w") as f,
+        patch.object(subprocess, "Popen", partial(subprocess.Popen, stdout=f)),
+        pytest.raises(RuntimeError, match="This is a test."),
+    ):
+        click.echo_via_pager(_test_gen_func_yields_then_fails())
+
+    assert "".join(writes) == "test", (
+        f"click should have written the yielded chunk before exception, got {writes!r}"
+    )
+
+
+@pytest.mark.stress
+@pytest.mark.skipif(WIN, reason="Different behavior on windows.")
+@pytest.mark.parametrize("_", range(1000))
+def test_stress_echo_via_pager_exception_cleanup(_, monkeypatch, tmp_path):
+    """Repeated exceptions during ``echo_via_pager`` must not leak subprocesses.
+
+    Regression coverage for the cleanup path in ``_pipepager``'s exception
+    handler (issue #2899, PR #3470). Each iteration spawns a real pager
+    subprocess, raises before any data is written and check there is no leak.
+    """
+    monkeypatch.setitem(os.environ, "PAGER", "cat")
+    monkeypatch.setattr(click._termui_impl, "isatty", lambda x: True)
+
+    spawned: list[subprocess.Popen] = []
+    real_popen = subprocess.Popen
+
+    def tracking_popen(*args, **kwargs):
+        p = real_popen(*args, **kwargs)
+        spawned.append(p)
+        return p
+
+    pager_out_tmp = tmp_path / "pager_out.txt"
+    with (
+        pager_out_tmp.open("w") as f,
+        patch.object(subprocess, "Popen", partial(tracking_popen, stdout=f)),
+        pytest.raises(RuntimeError),
+    ):
+        click.echo_via_pager(_test_gen_func_fails())
+
+    assert spawned, "pager subprocess was never started"
+    for p in spawned:
+        assert p.returncode is not None, "pager subprocess not reaped"
+
+
 def test_echo_color_flag(monkeypatch, capfd):
     isatty = True
     monkeypatch.setattr(click._compat, "isatty", lambda x: isatty)